Alternatives to fossil kerosene
As the number of flights continues to grow, ensuring planes are as efficient as possible and are capable of being powered by alternatives to fossil kerosene, is essential.
However, the right type of fuels need to be pursued. Using crop-based biofuels would cause negative effects such as driving deforestation or increasing food prices. Therefore the focus needs to be on Sustainable Aviation Fuels (SAF).
The biggest determinate as to whether a fuel is truly sustainable is the choice of feedstock. It is important to focus on biofuels which are advanced and therefore do not compete with food and forestry. Examples include municipal solid waste (MSW) and forestry residue. However these feedstocks are limited, and/or have competing uses. Oftentimes, these advanced fuels directly or indirectly compete with food and forestry. We therefore cannot rely on them to decarbonise aviation.
A potentially more abundant feedstock is renewable electricity, which can be used to produce synthetic kerosene, known as e-kerosene, when used to produce green hydrogen which is then combined with CO2 captured from the atmosphere. Renewable electricity is potentially far more abundant than the land needed for crop biofuels or feedstocks needed for advanced biofuels, and therefore should be the focus of efforts to decarbonise aviation.
To deliver savings in the short term, we will need to maximise the efficiency of traditional aircraft design. Unlike most other transport modes, there are no credible CO2 efficiency standards for aircraft design. It is sometimes argued that fuel savings are a sufficient incentive for aircraft manufacturers to maximise efficiencies, but in reality they face competing demands on cost and range. It is therefore important that regulators step in with more effective standards, and provide further incentives through more effective carbon pricing.
But this isn’t enough on its own. We will need zero-emissions airplanes if the sector is to decarbonise. This means planes which are powered by clean electricity or hydrogen produced using renewable energy. However, there are important barriers which should not be underestimated. For example, batteries are much heavier than kerosene, and all new aircraft designs face challenging certification processes to ensure safety. There will also be substantial development costs, including redesigning airports and retraining pilots. Again, cooperation between industry and regulators will be needed to develop such aircraft.
Zero-emission aircraft designs will likely take time to be deployed and may be limited to only short and medium-range flights. It is therefore important that an “all of the above” approach is pursued, whereby efficiencies from traditional aircraft are maximised, new fuels are developed, and governments support breakthrough aircraft designs.